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2 Sheets-Sheet 1.

. H H W W a Q Q m I Patented Sept. 27, 1892 m: min: nvzv'a cm, mamlmm, wmmnnn, o. c,

(No Model.)

G. E. SCRIBNER. TEST SYSTEM FOR MULTIPLE SWITCHBOARDS.

(No Model.) 2 Sheets-Sheet 2.

G. E. SGRIBNER. TEST SYSTEM FOR MULTIPLE SWITOHBOARDS.

No. 483,175. Patented Sept. 27, 1892.

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. UNITED STATES PATENT OFFICE.

CHARLES E. SCRIBNER, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE \VESTERN ELECTRIC COMPANY, OF SAME PLACE.

TEST SYSTEM FO R M U LTl PLE. SWITCH BOARDS.

SPECIFICATION forming part of Letters Patent No. 483,175, dated September 27, 1892.

Application filed December 5, 1891- Serial No. 414,134. (No model.)

To all whom it may concern: nunciator of the line with which cmnection Be it known that I, CHARLES E. SCRIBNER, is made. a citizen of the United States, residing at Chi- Referring now to Figs. 1 and 2, station 1 is cago, in the county of Cook and State of Illiconnected by a metallic circuit by limb a 5 nois, have invented a certain new and use with the springs of the different switches of fullmprovement in Test Systems for Multiple the line and by limb a with the metallic Switchboards, (Case No. 28-2,) of which the 501- frames or tubes of the same switches on the lowing is a full, clear, concise, and exact dedifferent switchboards. Between the differscription, reference being had to the accomout parts of the switch I) on this line of the [o panying drawings, formingapart of this specilast board a condenser c is included in circuit fication. with the individual annunciator b. The ca- My invention relates to telephone-exchange pacity of the condenser may he, say, one-tenth systems in which multiple switchboards are of a microfarad. The circuit of the line of employed; and its object is to so arrange the station 2 extends by the main wire (Z to the r 5 circuits that the resistance of the contacts of springs of the switches of this line, and after the several switches will be removed from the passing the condenser and individual annuncircuit of two connected lines, while at the ciator e f is connected by wire 9 with the same time individual annunciators of moderframes or tubes of the same switches of the ate resistance may be employed. line on the difierent switchboards, and thence 20 My invention consists more particularlyin to ground. The circuits of the operators outincluding a condenser in each circuit in confit, with the plugs h i and cords 7t Z, the telenection with the individual annunciator. phone m, the clearing-out annunciatorn, and

My invention will be more readily nnderwith the retardation-coil 0 and test-batteryp, stood by reference to the accompanying draware the same heretofore employed.

:5 ings, in which As before stated, the essential feature of Figure l is a diagram illustrative of three my invention is including a different contelephone-lines, two having metallic circuits denser in the circuit of each of the telephone and one having a grounded circuit, with two lines with each of the individual annunciaswitchboards, with the operators keyboard tors thereof, in order that when a line is con- 0 and telephone apparatus at each of the nected with another line by the operator its boards, the individual annnnciator of one of individual annunciator maybe removed from the grounded circuits being omitted for simthe circuit by a shunt through the bridgeplicity. Fig. 2, Sheet 2, is a more simple diawire between the cords, including the cleargrammatic illustration of the circuits of two ing-out annunciator, so that alternating our- 3 5 telephone-lines, one a metallic circuit and the rents sent over the line from the subscribers other a grounded circuit, each connected with station may not throw down the individual its series of switches distributed on different annunciator. In short, the condenser, being switchboards and each including a condenser included in circuit with the individual annunin circuit with the individual annunciator ciator, reduces the conductive capacity of the 0 thereof, the circuit of an operators outfit beportion of the circuit including the individual ing also illustrated. annunciator as compared with the conductive As is well known, individual annunciators capacity of the bridge=wire, including the of very high resistance-say three thousand clearing-out drop, so that when two lines are ohms-would be required in connection with connected together their individual annun- 45 the circuit shown if the condensers were ciators will not be thrown down by operating 5 omitted, in order that when connection is the generator at either subscribers station. made with a line the connection through the I have sometimes included a condenser in clearing-out drop, which ordinarily would be the bridge-wire and used a test-battery of of five hundred ohms, may be low enough by very high electro motive force-=-say thirty or 50 comparison to shunt out the individual anforty volts. This I have illustrated in Fig. :00

2, but not in Fig. 1. When the test-battery is small-say three to five volts, as shown in Fig. 1, its current would not be strong enough to operate an individual annunciator of theline upon which it was thrown, even though no condenser should be included in the circuit of the bridge-Wire of the clearing-out drop. If, however, the test-battery were of high electro-motive force, as described in connection with Fig. 2, current from the test-battery might be of sufficient strength to operate the individual annunciator if no means were provided for checking the flow of the current across the bridge-wire, including the clearing-out annunciator 'n. For greater caution I preferably employ a test-battery of considerable electro-motive force and place a condenser in the bridge-wire of the clearing-out annunciator.

My invention admits of various modifications, which will readily suggest themselves to those skilled in the art, and I therefore do not limit myself to the details of construction shown.

Having thus described my invention, I claim as new and desire to secure by Letters Patent- 1. The combination, with a telephone-line having one limb or portion thereof permanently connected with the springs of the switches of the line and by the other limb or portion thereof with the frames or test-pieces of the same switches, of a wire permanently connecting said limbs together at the central office, said connecting-wire including a condenser and an individual annunciator.

2. The combination, with a telephone-line extending from the subscribers station to the centraloffice,ofswitches upondiiferentswitchboards, each switch being provided with a switch lever and frame insulated from one another, one portion of the telephone-line being permanently connected with the springs of said switches and the other portion being connected with the frames or test-pieces thereof, a wire at the central ofiice connecting the two portions of telephone-line together, and an individual annunciator and a condenser included in said connecting-wire, substantially as and for the purpose specified.

3. The combination, with a telephone-line extending from the subscribers station to the centraloffice,ofswitchesupondiiferentswitchboards, each switch being provided with a switch lever and frame insulated from one another, one portion of the telephone-line being permanently connected with the springs of said switches and the other portion being connected with the frames or test-pieces thereof, a Wire at the central office connecting the two portions of telephone-line together, and an individual annunciator and condenser included in said wire, and switching apparatus consisting of pairs of double-pointed plugs and cords, one strand of said cords (the strand connecting the sleeves thereof) being con nected to ground through a retardation-coil and battery, a listening-in key for bridging the telephone between the strands, and a bridge-wire, including a clearing-out annunciator, permanently connected between said strands.

4. The combination, with a telephone-line extending from the subscribers station to the centraloflice,of switches upon differentswitchboards, each switch being provided with a switch lever and frame insulated from one another, one portion of the telephone-line being permanently connected with the springs of said switches and the other portion being connected with the frames or test-pieces thereof, a wire at the central office connecting the two portions of telephone-line together, and an individual annunciator and condenser included in said wire, and switching apparatus consisting of pairs of double-pointed plugs and cords, one strand of said cords (the strand connecting the sleeves thereof) being connected to ground through a retardation-coil and battery, a listening-in key for bridging the telephone between the strands, and a bridge-Wire, including a clearing-out annunciator and a condenser, permanently connected between said strands.

In witness whereof I hereunto subscribe my name this 25th day of November, A. D. 1891.

CHARLES E. SCRIBNER. Witnesses:

GEORGE L. CRAGG, GEORGE P. BARTON. 

